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Biochem > Module 9 - Electron Transport Chain > Flashcards

Module 9 - Electron Transport Chain Flashcards

1
Q

Electron transport chain is..

A

series of protein complexes embedded in mitochondrial membrane
○E- captured from donor molecules are transferred through these complexes

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2
Q

What are complexes found in the e transport chain

A

NADH dehydrogenase, succinate dehydrogenase, cytochrome c reductase, cytochrome c oxidase, ATP synthase

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3
Q

What are the mobible carrier involved in etc

A

ubiquinone and cytochrome c

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4
Q

What are other key components of ETC

A

NADH and its e-, H+ , O2, water and ADP and Pi which combine to make ATP

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5
Q

Give a breif overview of the electron transport chain

FUCK THIS QUESTION

A

●At start of e- transport chain two e- passed from NADH into NADH dehydrogenase complex
○One H for each e- coupled with this
●Next 2 e- transferred to ubiquinone
○Ubiquinone is called mobile transfer molecule which moves e- to cytochrome b-c1 complex to cytochrome c
●Cytochrome c then accepts each e- one at a time and one H+ pumped through complex as each e- is transferred
● Next in the cytochrome oxidase complex, 4 e- required that interact with molecular oxygen to form two water molecules
○Other 4 H+ are pumped across membrane
○This series of H+ pumping creates gradient
○The potential energy in this gradient is used by ATP synthase to make ATP from ADP and inorganic phosphate

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6
Q

What is the structure of the electron transport chain (protein compelces)

A

Made of 5 protein compleces embedded w/in inner mitochondrial membrane
Protein complex 1,2,3,4,5

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7
Q

What is role of the first complex

A
  • in general the role of the first complex is
    1. Accept 2 e- from NADH and shuttle them along
    2. Pump 4 protons out of mitochondrial matrix and into intermembrane space
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8
Q

What is the role of coenzyme Q and cytochrome c

A

● Coenzyme Q shuttles e- through complex 1 and 2 (causes transport of 4 H+) to complex III and cytochrome c shuttles e- from complex III to complex IV

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9
Q

Why do we need coenzyme Q and cytochrome c

A

electrons dont dissfuse well through hydrophobic interior of membrane
- COenzyme Q and cytochrome c are lipid soluble and can transport the electrond

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10
Q

Do protein complexes accept electrons? Why or why not

A
  • protein compelx doesnt, redox centres w/in protein complex accept electrons
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11
Q

What is the function of redox centers, where are they located

A

-Since protein complexes themselves arent reversible reduced/oxidized, redox centers can be reversible reduced and oxidizes (like Nad+ and NADH)

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12
Q

How many redox centers are in a protein complex

A

Proteins complexes contain a combination of two or more redox centers

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13
Q

What are the types redox centers in a protein complexes

A

○Fe-S clusters
○Copper (Cu)
○Cytochromes
○Coenzymes

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14
Q

What happens to the electrons on NADH and FADH (what complexes..)

A

NADH donates e- to complex I, complex I passes it to complex III then complex IV
FADH2 It donates its e- to complex II (which is logical and convenient since it’s already there anyways). Then complex II passes it along to complex III then complex IV

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15
Q

What is FADH2 in cirtric acid cycle

A

Electron donor but also coenzyme that is prosthetic group that’s covalently bound to enzyme succinate dehydrogenase which is part of complex II

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16
Q

What is shutte of electrons driven by

A
  • reduction of potentials of coenzymes and each individual redoc center until final e- acceptor (O2)
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17
Q

What is the final reduction

A

oxygen catalyzed by enzyme cytochrome oxidase making 2 H2O which is part of complex IV

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18
Q

What is reduction potential

A

Affinity something as for e-

19
Q

What is the relative reduction potential of NADH and Oxygen during the beginning of ETC

A

NADH has lowest reduction potential (least affinity for e-) whereas oxygen has highest reduction potential (highest affinity)

20
Q

What happens to the redox centers between NADH and oxygen

A

you pass from protein complex I to III to IV they have increasing reduction potential

21
Q

Describe what happens in Complex 1: NADH to Ubiquinone

A
  • NADH transfers 2 e- and 1H+ to complex 1
  • Complex 1 uses 2e- to pump 4 H+ from matrix into inter membrane space
  • Then the two e- are transfer to Coenzyme Q (QH2)
22
Q

Describe what happens in Complex 2: Succinate to Ubiquinone

A
  • FAD accept two e- from succinate and becomes FADH2
  • the electrons from FADH2 pass through iron-sulfur centers to ubiquinone (Coenzyme Q) (QH2)
  • IT DOES NOT PUMP PROTEONS
  • capture and donates protons
23
Q

Describe what happens in Complex 3: Ubiquinone to Cytochrome C oxidoreductase

A
  • Coenzyme Q’s reduce 2 molecules of cytochrome c
  • electrons pass through Iron sulfur clusters, cytochrome b and cytochrome c
  • Clearance of e- from reduced Quinones via Q cycle results in 4 H+ to be pumped into inter membrane space
24
Q

Describe Complex 4: Cytochrome C to O2

A
  • Four electrons (From cytochrome c) reduce 1 Molecule of oxygen to 2 molecules of water
  • Four protons are picked up from matrix for this process
  • ANother 2 H are passed from matrix into inter membrane space
25
Q

What happens each time electrons pass through protein complexes. What is it used for

A
  • each time e- pass through protein complex w/ lower reduction potential to redox centre w/ high reduction potential; energy is released
  • The complex uses the energy released to drive proton pumping mechanism that pumps proteins out of matrix and into inter membrane space
26
Q

How many Protons does each complex pump out per pair of electrons

A

●Complex I and III each pump 4 protons for each pair of electrons that pass through and Complex iV pumps out only two protons and Complex II pumps nothing

27
Q

What is the chemiosmotic gradient

A

The removal of protons from the matrix and deposition of protons in the intermembrane space creates a concentration difference of protons across the inner membrane (chemoosmotic gradient)

28
Q

What is the only way for protons to move to inner mitochondrial membrane

A

Through specific transport protein

29
Q

What is the gradient in nature

A

Electrochemical

30
Q

Why is it called electrochemical in nature

A

○chemical in nature in terms of creating a lower pH of the outside of the inner membrane
○‘electrical’ in natural because of the positive charge of the protons needed to reach equilibrium by entering mitochondrial matrix where charge is negative

31
Q

What does the chemiosmotic gradient able to do

A
  • it has potential energy stored

- energy is used to drive synthesis of ATP by process called oxidative phosphorylation of ADP to ATP in the complex V

32
Q

In What complex does the oxidative phosphoyrlation of ADP occur

A

ATP, is catalyzed by complex V which is also known as F1-F0 ATP synthase that is composed of multiple subunits

33
Q

Describe the strucutre of Complex V

A
  • aka F1-F0 ATP synthase composed of multiple subunits
  • F0 subunit: Protein channel that spans inner mitochondrial membrane, responsible for allowing protons to enter matrix. Integral membrane protein. Its energy is transferred to F1 to catalyze phosphorylation
  • rotates when a new hydrogen ion enters, once three protons/h enter the matrix space, there is enough energy in the ATP synthase complex to synthesize one ATP
  • F1 subunit: bulbous portion on matrix side of inner membrane. Has the ATP synthase enzyme. Its soluble in maxtrix and individually catalyzes the hydrolysis of ATP.
  • F1+F0 are connected by protein stalk
  • looks like mushroom protruding into the matrix on the inside of the inner membrane.
34
Q

How does complex V work?

A

● One hydrogen ion enters the ATP synthase complex from the intermembrane space a second hydrogen ion leaves it on the matrix space
● Upper part of the ATP synthase complex rotates when a new hydrogen ion enters, once three protons/h enter the matrix space, there is enough energy in the ATP synthase complex to synthesize one ATP
○ Energy in the hydrogen ion gradient is used to make ATP
● Proton enters ATP synthase and exits into the matrix space
● Once three more h atoms have crossed the membrane, ATP is made
● Keeps going until there is an equal number of protons on each side of the inner membrane, no more energy left
● In biological systems, a gradient is always maintained
○ Mitochondrial hydrogen ion gradient is generated as electrons pass through three membrane complexes

35
Q

How is the gradient maintained

A

Mitochondrial hydrogen ion gradient is generated as electrons pass through three membrane complexes

36
Q

What drives the ATP synthase in F1 subunit

A

When protons pass through F0 channel and stalk from outside to inside of matrix
○proton serves to drive the molecular motor of the ATP synthase which has an ADP and an inorganic phosphate (Pi) present in the active cell
○Proton actually drives the conformation change in the active site and drives the catalysis of the formation of a new high energy phosphoanhydride bond in ATP

37
Q

How many protons are pumped out as a result of NADH

A

● Each NADH that donates its electrons to the electron transport chain at complex I, a total of 10 protons are pumped out

38
Q

How many protons are pumped out as a result of FAHD2

A

● Each FAH2 that donates its electrons through complex II, a total of only 6 protons are pumped out

39
Q

How many ATP can NADH yeild and why

A

3 ATP (per mole of O2 consumed) due to 10 protons pumped out (Need 3/ATP)

40
Q

How many ATP can FADH2 yield

A

2 ATP (per mole of O2 consumed) due to 6 protons

41
Q

How many ATP are generated per glucose molecule that is oxidized (and from which processes)

A

38 ATP

From Glucose to Pyruvate and Pyruvate to Acetyl CoA and then citric acid cycle

42
Q

How does NADH from glycolysis reach the mitochondria Matric

A
  • It never is able to cross into the inner membrane

there is no transport for NADH

43
Q

What are mechanism by which NADH can donate its electrons to transverse into the membrane. Explain them

A
  • Two pathways that provide electrons for NADH generated in the cytosol to ETC:
  • Glycerol-3-phosphate
  • Malate aspartate shuttle

Biochem (7 decks)

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